In recent years, experimental demonstration of ferroelectric tunnel junctions (FTJ) based on perovskite tunnel barriers has been reported. However, integrating these perovskite materials into conventional silicon memory technology remains challenging due to their lack of compatibility with the complementary metal oxide semiconductor process (CMOS). This communication reports the fabrication of an FTJ based on a CMOS-compatible tunnel barrier HfZrO (6 unit cells thick) on an equally CMOS-compatible TiN electrode. Analysis of the FTJ by grazing angle incidence X-ray diffraction confirmed the formation of the noncentrosymmetric orthorhombic phase (Pbc2, ferroelectric phase). The FTJ characterization is followed by the reconstruction of the electrostatic potential profile in the as-grown TiN/HfZrO/Pt heterostructure. A direct tunneling current model across a trapezoidal barrier was used to correlate the electronic and electrical properties of our FTJ devices. The good agreement between the experimental and theoretical model attests to the tunneling electroresistance effect (TER) in our FTJ device. A TER ratio of ∼15 was calculated for the present FTJ device at low read voltage (+0.2 V). This study suggests that HfZrO is a promising candidate for integration into conventional Si memory technology.

The present work reports the fabrication of a ferroelectric tunnel junction based on a CMOS compatible 2.8 nm-thick Hf0.5Zr0.5O2 tunnel barrier. It presents a comprehensive study of the electronic properties of the Pt/Hf0.5Zr0.5O2/Pt system by X-ray photoelectron and UV-Visible spectroscopies. Furthermore, two different scanning probe techniques (Piezoresponse Force Microscopy and conductive-AFM) were used to demonstrate the ferroelectric behavior of the ultrathin Hf0.5Zr0.5O2 layer as well as the typical current-voltage characteristic of a ferroelectric tunnel junction device. Finally, a direct tunneling model across symmetric barriers was used to correlate electronic and electric transport properties of the ferroelectric tunnel junction system, demonstrating a large tunnel electroresistance effect with a tunneling electroresistance effect ratio of 20.

Titanium dioxide thin films (30 nm) are deposited on platinized substrates by atomic layer deposition and locally studied by conductive atomic force microscopy showing repetitive bipolar resistive switching. Experiments using macroscopic copper top electrodes, which are electroformed, bipolar switched, and removed again from the TiO2–Pt stack, prove the formation of local conductive filaments with bipolar switching properties. The localized filaments can be switched repetitively with a resistance ratio of 30. Our findings underline that Cu diffusion and the formation of filaments are the major mechanism for the resistive switching in Cu/TiO2/Pt cells.

We report on the electroforming in resistively switching nanocrosspoint devices made of a reactively sputtered TiO2 thin film between Pt and Ti/Pt electrodes, respectively. As most resistance switching materials, TiO2 needs to be electroformed before it can be switched. This paper presents and compares current and voltage controlled electroforming with regard to the polarity. We show that a current-driven electroforming with negative polarities leads into the switchable high resistive state without need for a current compliance. These devices show an improved stability and reliability in bipolar resistive switching performance.

The collagen meshwork plays a central role in the functioning of a range of tissues including cartilage, tendon, arteries, skin, bone and ligament. Because of its importance in function, it is of considerable interest for studying development, disease and regeneration processes. Here, we have used second harmonic generation (SHG) to image human tissues on the hundreds of micron scale, and developed a numerical model to quantitatively interpret the images in terms of the underlying collagen structure on the tens to hundreds of nanometer scale. Focusing on osteoarthritic changes in cartilage, we have demonstrated that this combination of polarized SHG imaging and numerical modeling can estimate fibril diameter, filling fraction, orientation and bundling. This extends SHG microscopy from a qualitative to quantitative imaging technique, providing a label-free and non-destructive platform for characterizing the extracellular matrix that can expand our understanding of the structural mechanisms in disease.